What do you mean by Medium Earth Orbit (MEO)?

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Aug 30, 2022

Medium Earth orbits (MEO) are Earth-centered orbits with an altitude from 2000 km to 35,786 km above the surface of the Earth. The most prominent satellites traversing the MEO are the GPS & the Galileo Satellite constellations which power navigation across the world. 

The MEO orbit is located in the Van Halen Radiation belt which is a zone of energetically charged particles that are created due to solar winds by the sun and are captured in the region by the earth’s magnetic pull. This region is very dangerous for humans, which is the primary reason for the nonexistence of ISS (International Space stations) or habitable space stations in the MEO as the astronauts are susceptible to high amounts of radiation.

Satellites orbiting in the MEO are highly shielded with materials such as Gold, aluminum, and Kevlar which are stacked in layers that keep the radiation at bay. It is advised that Satellites or manned space missions that need to pass the MEO and venture into space, must do so by crossing the MEO at a very high speed with a maximum thrust thereby limiting the time spent in the Van Halen radiation zone.

For a satellite to remain in an MEO orbit, it needs to travel at a speed of 7,000 miles per hour (3.13 km per second). If the satellite’s Orbital Velocity is higher than the optimal value, it faces the risk of flying out of orbit and into space, rendering the satellite out of bounds. Additionally, If the orbital velocity is kept too low, the satellite will be pulled back to earth due to gravity causing it to crash and burn. Hence, if the correct Orbital velocity is maintained the gravity of the earth balances the inertia of the satellite, pulling it down to the earth’s surface just enough to enable the satellite to traverse in its intended orbit. At Higher altitudes, the speed required to keep a satellite in an orbit changes. The speed of the satellite in an orbit is inversely proportional to the altitude from the earth’s surface.

MEO is the core of navigation systems that make communication and navigation possible on Earth. The number of satellites that are required for earth’s coverage is less when compared with LEO (Low earth orbits) due to the increased coverage. A Satellite in an MEO completes around 1-2 Orbits in a day. To achieve a 12-hour orbit (2 orbits in a day), an MEO Satellite must be placed at a height of 20,200 km from the earth’s surface. Hence most communication and Navigation satellites are placed in and around this distance from the earth. 

Global Navigation Satellite Systems (GNSS) is the network of satellites that broadcast orbital information to be used for communication and navigation to the earth’s base station on the surface. At present GNSS includes two fully operational Global systems. Some examples of GNSS satellites include the United States Global Positioning System (GPS) (Altitude of 20,200 kilometers), The Russian Federation’s GLONASS (Altitude of 19,100 kilometers), and Europe’s Satellite Navigation system known as Galileo (Altitude of 23,222 kilometers). Communication Satellites covering the North and South Pole also revolve around MEO.

Key Parameters of Medium Earth Orbits

Parameters

MEO Attributes

The altitude of MEO From Earth

2000 km - 35,786 km

Orbital Velocity for a satellite in MEO

7,000 mph (3.13 km/s)

Orbits Completed in a Day for a Satellite

1-2 Orbits per day

Satellites Needed

10-15 for Global Coverage

Satellite Life

10-15 Years

Propagation Loss

Medium

Network Complexity

Medium

Transmission Delay

100-150 ms

Broadband Capability

Poor